Side effects of clozapine in older adults with treatment-resistant schizophrenia compared to younger adults.

Abstract

To study the differences in side effects of clozapine between older adults aged ≥55years and younger adults aged 18-55years with treatment-resistant schizophrenia. A retrospective cohort study in a large mental health institute in the Netherlands. All patients diagnosed with treatment-resistant schizophrenia who started with clozapine between 2011 and 2020 (N=284) were included. We compared the number and type of side effects reported in the electronic patient files as well as the number of treatment discontinuations and the time until discontinuation, both due to side effects, of older adults versus younger adults. In the younger age group (N=183), the number of reported side effects was significantly higher in the first 3months of treatment (Mann-Whitney U=7341.5, p=0.004) and after those 3months (Mann-Whitney U=5668.5, p<0.001) compared with the number reported in the older age group (N=101). Sedation, hypersalivation, dizziness, tachycardia, heartburn, nausea, weight gain, and constipation were reported significantly more often in the younger age group, and only extrapyramidal symptoms were reported significantly more often in the older age group. There was no significant difference in the number of treatment discontinuations due to side effects (23% vs. 21.8%, Chi-2=0.051, df=1, p=0.821) and time until discontinuation due to side effects (b=0.091, SE=0.335, p=0.798) between younger and older adults. Side effects of clozapine were reported significantly less often in older patients compared with younger patients. Older patients did not discontinue treatment due to side effects more often or earlier than younger patients. Older patients with schizophrenia may not be more vulnerable to side effects than younger adults.